JPH11201256A - Actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent generation of a moving defective of a ball by disposing a freely movable ball along a ball rolling surface of a screw shaft on a nut member onto which the revolved and driven screw shaft is screwed and holding this ball so that the ball may not move and may rotate for the nut member. SOLUTION: An actuator to be used as a carrier device of a work has a ball screw 34 to be rotated by a motor and a nut member 36 onto which this ball screw 34 is screwed and which moves in the direction of the arrow A for the ball screw 34. In this nut member 36, a freely slidable ball 40 is disposed along a ball rolling surface 38 of the ball screw 34 and this ball 40 is held by a holding means 42 so that the ball may not move and may rotate for the nut member 36. The holding means 42 is provided with an oil supply means 56 for performing fluid lubrication and elastic fluid lubrication between each recessed part 54 and the ball 40. On an inner peripheral surface 52 of the nut member 36, a ring-shaped groove part 68 is formed and a scraper 70 is fixed to this groove part 68.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator having a screw shaft which is driven to rotate and a nut member which is screwed and relatively moved.

[0002]

2. Description of the Related Art In general, an actuator having a ball screw is widely used for various purposes as a work positioning device, a transfer device and the like.

For example, as shown in FIG. 5, a conventional actuator 2 includes a motor 4 as a drive source, and a ball screw (screw shaft) 6 is connected to a drive shaft of the motor 4. The ball screw 6 extends in the longitudinal direction of the body 8, and both ends thereof are rotatably supported by the body 8 via support blocks 10a and 10b. The ball screw 6 is screwed into a nut member 14 incorporated in the moving table 12.

As shown in FIG. 6, a ball rolling surface 16 is provided on the ball screw 6, while a thread groove 18 corresponding to the ball rolling surface 16 is formed on the nut member 14. The screw groove 18 is formed endless via a return passage 20, and a plurality of balls 22 are arranged between the screw groove 18 and the ball rolling surface 16 and in the return passage 20.

In the actuator 2 described above, when the ball screw 6 is rotated under the action of the motor 4, the ball rolling surface 16 of the ball screw 6 and the thread groove 1 of the nut member 14 are formed.
The nut member 14 moves in the axial direction of the ball screw 6 via a plurality of balls 22 provided integrally with the ball screw 6. At this time, the ball 22 rolls on the ball rolling surface 16 and the thread groove 18, moves from the upstream side to the downstream side of the thread groove 18, and then returns to the thread groove 18 via the return passage 20. It is returned to the upstream side.

[0006]

By the way, in order to move the nut member 14 accurately and smoothly in the axial direction of the ball screw 6, the return passage 20 is provided from between the ball rolling surface 16 and the thread groove 18. It is necessary to smoothly send the ball 22 to be sent out again between the ball rolling surface 16 and the thread groove 18. For this reason, especially the nut member 1
It has been pointed out that the processing accuracy of No. 4 must be kept high, and the manufacturing cost of the nut member 14 rises considerably. Further, clogging of the ball 22 is likely to occur near the entrance of the return passage 20, and the nut member 14
There is a problem in that it is difficult to always move the object smoothly and with high precision.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an actuator capable of constantly and accurately moving a nut member smoothly with a simple structure.

[0008]

In order to solve the above-mentioned problems, in the actuator according to the present invention, when a screw shaft is driven to rotate under the action of a drive source, the screw shaft is screwed to the screw shaft via a ball. The nut member to be moved moves along the axial direction of the screw shaft. At this time, the ball is held immovable and rotatable with respect to the nut member, and the ball does not circulate in the nut member.

Therefore, there is no need to provide a ball return passage in the nut member, and this nut member can be manufactured simply and efficiently. Moreover, since the ball is held immovably with respect to the nut member, the ball does not clog in the nut member. With this, the nut member is always moved in the axial direction of the screw shaft.
It is possible to move smoothly and reliably.

[0010] The holding means is formed on the inner peripheral surface of the nut member and accommodates the ball in a non-movable state, and performs fluid lubrication or elastic lubrication between the spherical recess and the ball. Oil supply means for performing the operation. For this reason, the spherical concave portion and the friction surface of the ball are reliably separated by the oil film, so that the occurrence of wear can be reliably prevented, and the movement of the nut member can be more smoothly performed.

Further, an elastic claw member which is in sliding contact with the ball is provided on the inner peripheral surface of the nut member. Therefore,
Even if dust or the like adheres to the ball from the screw shaft side, the dust is effectively removed via the elastic claw member, and the dust does not enter between the ball and the spherical concave portion. Thereby, smooth movement of the nut member is ensured.

[0012]

FIG. 1 is a schematic perspective explanatory view of an actuator 30 according to an embodiment of the present invention, and FIG.
FIG. 3 is an explanatory view of a main part longitudinal section of the actuator 30, and FIG. 3 is an explanatory view of a main part of the actuator 30 cut along a ball arrangement position.

The actuator 30 is a motor (drive source)
Ball screw (screw shaft) that is connected to 32 and transmits power
34, a nut member 36 with which the ball screw 34 is screwed and which moves in the direction of arrow A with respect to the ball screw 34;
A ball 40 disposed on the nut member 36 and capable of rolling or sliding along a ball rolling surface 38 of the ball screw 34; and the ball 40 being immovable and rotating with respect to the nut member 36. And holding means 42 for holding as possible.

Both ends of the ball screw 34 are supported on a support 44a,
The support bases 44a, 44b are rotatably supported by support bearings 46a, 46b provided on the support bases 44a, 44b.
b is fixed to the main body 48. Nut member 36
Constitutes a movable table, and a table (not shown) is detachably fixed on the nut member 36.

As shown in FIGS. 2 and 3, a through hole 50 for inserting the ball screw 34 is formed at the center of the nut member 36, and the inner peripheral surface 5 of the through hole 50 is formed.
2, a spherical concave portion 54 constituting the holding means 42 is formed. The plurality of concave portions 54 are provided on the inner peripheral surface 52 of the nut member 36 at a predetermined angular interval corresponding to the pitch of the ball rolling surface 38 of the ball screw 34.

The holding means 42 is provided with each recess 54 and the ball 40
And oil supply means 56 for performing fluid lubrication or elastohydrodynamic lubrication between them. The oil supply means 56 includes the nut member 36
The oil supply port 58 is fixed to the oil supply port 58. A pipe 60 attached to the oil supply port 58 communicates with an oil supply source (not shown). An oil supply member 62 made of a porous polymer is provided downstream of the oil supply port 58, and an oil passage 64 communicates with the oil supply member 62. The oil passage 64 has a plurality of holes 66 that branch off at predetermined positions and communicate with the recesses 54.

As shown in FIG. 4, a ring-shaped groove 68 is formed on the inner peripheral surface 52 of the nut member 36 around each recess 54, and a scraper (elastic claw member) 7 is formed in the groove 68.
0 is fixed by press-fitting or bonding. Scraper 7
Numeral 0 is made of, for example, a resin such as ultrahigh molecular weight polyethylene, elastomer, or PTFE, and the tip side thereof is always in sliding contact with the outer peripheral surface of the ball 40.

The actuator 30 constructed as described above
Will be described below.

First, when the ball screw 34 is driven to rotate by the driving action of the motor 32, the plurality of ball rolling surfaces 38 of the ball screw 34 and the recesses 54 of the nut member 36 are integrally arranged. The nut member 36 moves in the direction of the arrow A via the ball 40.

At this time, in this embodiment, the ball 40 is
While rolling (or sliding) along the ball rolling surface 38 of the ball screw 34, only sliding by rotation is performed in the concave portion 54 of the nut member 36. For this reason, the ball 40 rolls along the inner peripheral surface 52 of the nut member 36 and is once clogged or has a poor return as compared with the conventional structure which is returned from the inner peripheral surface 52 via the return passage. Etc. are not caused. Thereby, the nut member 36
Is along the axial direction (arrow A direction) of the ball screw 34,
There is an effect that it is possible to always move smoothly and with high precision.

In this embodiment, the nut member 36 is provided with oil supply means 56, and the oil supply member 62 is filled with oil 72 from a not-shown oil supply source via a pipe 60. As shown in FIG. 4, the oil 72 is supplied from the oil passage 64 to the space between the concave portion 54 and the ball 40 via each hole 66, and an oil film 74 having a predetermined thickness is formed. Therefore, fluid lubrication or elastic fluid lubrication is performed between the ball 40 and the concave portion 54, so that the wear is reliably prevented, and the movement of the nut member 36 in the direction of the arrow A is further smoothed. is there.

Furthermore, the inner peripheral surface 52 of the nut member 36
Is provided with a resin scraper 70 surrounding each recess 54, and the tip of the scraper 70 is
0 is always in sliding contact with the outer peripheral surface. Therefore, even if dust or the like adheres to the outer peripheral surface of the ball 40 from the ball rolling surface 38 side when the ball 40 rolls along the ball rolling surface 38 of the ball screw 34, the action of the scraper 70 It is possible to reliably prevent the dust from entering the recess 54 below. This reliably prevents dust or the like from entering between the concave portion 54 and the ball 40 to damage the inner wall surface of the concave portion 54 and prevent the nut member 36 from being smoothly moved in the direction of arrow A. It becomes possible to do.

In this embodiment, the case where the ball 40 rolls along the ball rolling surface 38 of the ball screw 34 has been described. However, when the ball 40 slides on the ball rolling surface 38, Will have the same effect.

[0024]

As described above, in the actuator according to the present invention, the nut member on which the screw shaft rotationally driven under the action of the drive source is screwed moves along the ball rolling surface of the screw shaft. A free ball is provided, and the ball is immovably and rotatably held by the nut member under the action of the holding means. For this reason, the ball does not roll in the nut member, and the ball is held at a predetermined position with respect to the nut member. Can be. Thereby, the nut member can always move smoothly and accurately in the axial direction of the screw shaft.

[Brief description of the drawings]

FIG. 1 is a schematic perspective explanatory view of an actuator according to an embodiment of the present invention.

FIG. 2 is an explanatory longitudinal sectional view of a main part of the actuator.

FIG. 3 is an explanatory view in which a main part of the actuator is cut along a ball arrangement position.

FIG. 4 is a partially enlarged explanatory view of a holding means constituting the actuator.

FIG. 5 is an explanatory perspective view of an actuator according to the related art.

FIG. 6 is an explanatory longitudinal sectional view of a main part of an actuator according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 30 ... Actuator 32 ... Motor 34 ... Ball screw 36 ... Nut member 38 ... Ball rolling surface 40 ... Ball 42 ... Holding means 54 ... Depression 56 ... Oil supply means 64 ... Oil passage 70 ... Scraper

Claims (3)

[Claims] A screw shaft connected to a drive source and driven to rotate; a nut member with which the screw shaft is screwed and relatively moved with respect to the screw shaft; An actuator comprising: a ball movable along a ball rolling surface of the screw shaft; and holding means for holding the ball immovably and rotatably with respect to the nut member. 2. The actuator according to claim 1, wherein
The holding means is formed on an inner peripheral surface of the nut member,
An actuator, comprising: a spherical concave portion that accommodates the ball in a non-movable state; and oil supply means for performing fluid lubrication or elastic fluid lubrication between the spherical concave portion and the ball. 3. The actuator according to claim 2, wherein
An actuator, wherein an inner surface of the nut member is provided with an elastic claw member that slides on the ball disposed in the spherical concave portion.